The contrast enhanced ultrasound is one of the image diagnosis methods which can provide high sensitivity image of a blood vessel to which a contrast medium has been administered. At present, in Japan, use of a contrast medium Sonazoid has been approved for liver diagnosis. The contrast medium Sonazoid is used for differentiation of a hepatic tumor.
In the case of a liver diagnosis, existence or absence of a tumor is identified first. In an ultrasound image, the tumor can be identified as a hypoechoic region or a hyperechoic region. Subsequently, the contrast of the tumor is enhanced with administration of the contrast medium.
Currently, the type determination of the tumor is performed based on the subjective judgment of a reader of the ultrasound image, and thus a problem exists that the diagnosis result depends on the reader.
In view of the problem, an objective differentiation method has been disclosed in which the differentiation is performed based on time-sequence variation in two feature values, which are average brightness and the standard deviation, of a tumor region (e.g. Patent Literature (PTL) 1).
According to the technique disclosed in PTL 1, three circles each of which is different in size and includes a tumor are set. The time waveform of the feature value of each of the circle is compared with the typical waveform of each of the types to determine the type based on the typical waveform that best resembles the time waveform. In each of the time phases, the tumor type that is most similar to the feature value of each of the three circles is determined. Then, the tumor type is determined to the type that occurs most.